1. Field of the Invention
The present invention relates to detection of an indicated position on a display screen that is indicated by a user.
2. Description of the Related Art
In a presentation using a projector for displaying an image supplied from a computer, the presenter often uses a pointing rod or his own finger to indicate a position on the displayed image on a screen. However, if the presenter wants to cause the computer or the projector to perform some processing using the indicated position, such as putting a mouse pointer on the indicated position, he must use a pointing device, such as a mouse, to make the change. It will be convenient for the presenter if the indicated position on the image is automatically detected by the presentation system.
An object of the present invention is to detect an indicated position on a display screen that is indicated by a presenter.
In order to attain at least part of the above and related objects of the present invention, there is provided a method of detecting an indicated position on a display screen that is indicated by a user. The method comprises the steps of: (a) capturing an image of the display screen that includes the indicated position, the captured image including a plurality of high resolution pixels; (b) producing a low resolution image with lower resolution than the captured image based on the captured image, the low resolution image including a plurality of low resolution pixels, each low resolution pixel being associated with a unit area within the captured image, the unit area including a predetermined number of high resolution pixels; (c) finding a low resolution pixel corresponding to the indicated position within the low resolution image; and (d) finding the indicated position within the captured image based on a unit area that is associated with the low resolution pixel corresponding to the indicated position. A resolution of the low resolution image is determined by finding integers A and B so that a value f given by Equation (1) is at a minimum:                     f        =                                            X              xc3x97              Y                                      A              xc3x97              B                                +                      A            xc3x97            B                                              (        1        )            
where X denotes a number of high resolution pixels of the captured image in a horizontal direction, Y denotes a number of high resolution pixels of the captured image in a vertical direction, and A denotes a number of high resolution pixels of the unit area in the horizontal direction, A being a divisor of X, and B denotes a number of high resolution pixels of the unit area in the vertical direction, B being a divisor of Y.
When finding an indicated position within the low resolution image, in the worst case, it may be necessary to check all of the X/Axc3x97Y/B pixels within the low resolution image. Similarly, when finding the pixel that correspond to the indicated position in a unit area of Axc3x97B pixels within the captured high resolution image, it may be necessary to check all of the Axc3x97B pixels. The above Equation (1) expresses the worst case value f of the number of pixels to be checked when assuming this kind of worst case scenario.
According to the present invention, the resolution of the low resolution image is determined so that the worst case reference pixel count f will be at a minimum, so it is possible to find the indicated position faster than in the case where the indicated position on a display screen is detected based only on a captured high resolution image.
In a preferred embodiment, the resolution of the low resolution image is determined by finding the integers A and B from among combinations of integers Ai and Bj satisfying Equation (2):                     0.5        ≤                              A            i                                B            j                          ≤        1.5                            (        2        )            
where Ai are divisors of X and Bj are divisors of Y.
In another embodiment, the resolution of the low resolution image is determined by finding the integers A and B from among combinations of integers Ai and Bj satisfying Equation (3):                               Y          X                ≤                              A            i                                B            j                          ≤                  X          Y                                    (        3        )            
where Ai are divisors of X and Bj are divisors of Y.
The resolution of the low resolution image may be determined by finding the integers A and B from among combinations of integers Ai and Bj which are equal to each other where Ai are divisors of X and Bj are divisors of Y.
The present invention can be realized in various embodiments as follows:
(1) A method and an apparatus for determining a resolution of a low resolution image;
(2) A method and an apparatus for detecting an indicated position;
(3) A display method a display apparatus utilizing the indicated position detection method or apparatus;
(4) A computer program for causing a computer to implement the functions of these methods and apparatus; and
(5) A storage medium that stores the computer program.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.